Men have friendships with mostly women for many reasons. One is to stroke their ego. It makes them feel good to be surrounded by women rather than bonding with men. This gives them a sense of power. Some men just generally like the company of women to that of men. This is hard to define since men usually need to bond with other men. Some men really do relate better to women. In the end I think there is always some ego involved in having all female friends. Of course he is going to say there isn't. You know if he is trustworthy or not. Just make sure he respects you when he has these friends. If you think he is crossing boundaries that shouldn't be crossed it is up to you to decide what you want to do. You have to decide if you are comfortable with this arrangement. It tests trust and whether he is being appropriate. It is up to you to decide if his friendships are appropriate.